Mechanical underfeed stoker.



C. ERITH. MECHANICAL UNDERFEED STOKER. APPLICATION FILED JAN. 13. m5.

1,298,189. Patented Mar. 25,1919.

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MECHANICAL UNDERFEED STOKER. APPLICATION FILED JAN. 13. 1915.

1 ,298,189. Patented Mar. 25,1919.

6 SHEETS--SHEET 2.

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MECHANICAL UNDERFEED STOKER.

APPLICATION FILED JAN. 13. I915.

1,298,189. Patented Mar. 25,1919.

6 SHEETS-SHEET 3- C. ERITH.

MECHANICAL UNDERFEED STOKER. APPLICATION fltED JANA-3.19M.

1,298,189. Patented Mar. 25,1919.

6 SHEETS-SHEET 4- ZJ/ww C. ERITH.

MECHANICAL UNDERFEED STOKER- APPLICATION FILED JAN.13. l9l5.

1,298,189. Patented Mar. 25,1919.

6 SHEETS-SHEET 5- C. ERITH.

MECHANICAL UNDERFEED STOKER. {\PPLICATION FILED MN- 13. i915- 6 SHEETSSHEET O.

I hay/22w? iMlz/kdisew Ag (id/7c: r h/A CHARLES ERITH, OF LONDON, ENGLAN'D.

MECHANICAL UNDERFEED STOKER.

Specification of Letters Patent.

Patented Mar. 25, 1919.

Application filed January 13, 1915. Serial No. 1,907.

To all whom it may concern:

Be it known that I, CHARLES ERITH, a subject of the King of Great Britain, residing at 70 Gracechurch street, in the city and county of London, England, have invented certain new and useful Improvements in or Relatin to Mechanical Underfeed Stokers, of whic the following is a specification.

' This invention relates to mechanical underfeed stokers as employed in boiler and other furnaces wherein the fuel is fed by reciprocating plungers into troughs or retorts whence it rises into the zone of combustion and in which furnaces the air for combustion is delivered under pressure into the fire through twyers placed along the sides of the fuel retorts. One object of my invention is to simplify the construction and operation of such stokers, thereby reducing the working cost and upkeep charges. Another object is to provide for continuously discharging the incombustible residue to the ashpit while maintaining a seal against the inflow of excess air at the point of discharge. A further object is to enable a steady steam pressure to be maintained when working a range of boil ers at varying loads.

According to the invention the fan or fans and fuel feeding plungers are actuated by a variable speed motor in such a manner t at while the fan or fans are continuously rotated, the crank shaft connected to the plungers may be advanced intermittently and in uniform, but variable steps as may be re quired. Each stoker will preferably be provided with a separate fan thus avoiding the necessity of employing an air duct or conduit with branch pipes to each stoker. Means are also provided whereby, as the incombustible residue or ash is advanced on to the ashplate, the area of the ash-opening may be varied according to the percentage of ash in the fuel and thereby obviate the excess inflow of air into the furnace from the ashpit. The supply of fuel and air in correct proportions to the retorts is controlled so that the rate of combustion may be automatically varied in response to and in accordance with the demand on the boilers for steam.

In order that the invention may be clearly understood and readily carried into effect the same will now be 111016' fully described by the aid of the accompanying drawings, in which Figure 1 is a sectional series of furnaces fitte lan of a range or with underfeed stokers of the side-cleaning type and showing the usual arrangement of fan and air ducts.

Fig. 2 is a cross-section of one of the furnaces shown in Fig. 1.

Fig. 3 is a similar view to Fig. 1 showing a series of furnaces fitted with underfeed stokers of the rear cleaning type, each stoker being provided with a separate fan for supplying air direct, as preferred.

Fig. 4 is a longitudinal section of one of the furnaces indicated in Fig. 3 and also shows the speed regulating means.

Fig. 5 is a side elevation of the gear for actuating and controlling the fuel feeding plungers.

Fig. 5 is an enlarged detailed view of Fig. 5 hereinafter fully described.

Fig. 6 is an end elevation, and

Fig. 7 a horizontal section of Fig. 5.

Fig. 8 shows the regulator as applied for controlling the steam admission valve of a turbine which constitutes the motor for driving the fan or fans and fuel feeding plungers.

(1 indicates the motor or turbine which drives the fan I) for supplying air through the main duct or conduit b and branch pipes b to the furnaces, and for actuating the reciprocating and intermittently operated fuel feeding plungers c.

In the side-cleaning type of underfeed stoker, shown by Figs. 1 and 2, the reciprocating plungers 0 feed'the fuel to the retorts d whence it rises over the twyers e, the incombustible residue or ash accumulating on the side plates f, from which the ash is periodically withdrawn. Hitherto side cleaning underfeed stokers with reciprocating plungers have been operated by intermittently actuated steam engines, that is to say, each plunger has been driven by a piston to which steam is admitted at intervals for each charging and return stroke of the plunger. In one such arrangement valve mechanism is employed for controlling the intermittent admission of steam to a series of such stokers. Experience shows, however, that there is a tendency for steam to leak past the valves and pistons when they are at rest, and also the losses in condensation and leakage in the steam pipes are often considerable, while the valve mechanism is necessarily complicated and costly. With the improve arrangement of ar, the crank shaft 71. for transmitting motion to the plungers c is actuated by means of spur wheels z and ratchet and pawl mechanism j, the pawl being carried by a lever is attached to a connecting rod Z which in turn connects with a sprocket -m driven by chain or other earing from the motor a. As shown in the (fi'awings the motor may drive on to a shaft 11.. provided with another sprocket or chain wheel n which in turn transmits motion by means of the chain 0 to the sprocket m (Fig. 5).

In the rear cleaning type of underfeed stoker indicated by Figs. 3 and 4 each fur-- naceis provided with its individual fan 6 while I also employ my improved driving mechanism of a kind similar to that deing underfeed stokers it has hithertoybeen.

usual'to connect the multiple fuel feeding plungers of each unit to a crank-shaft and to drive this crank-shaft very slowly but continuously from a high-speed steam en-' gine, employing costly double-worm reduction gearingtogether with a clutch for. each such stoker. In. large unit stokers of'this class, two, three or more worm-gears and clutches are used. If more than one stoker unit is driven from the same engine then each unit requires in addition variable speed gear. A series of small steamengines for stokers and fan'or fans-, is very unecoi momical in steam, especially when the exratchet and spur ratchet 'vvheel haust steam is discharged to,atmos'phere, and thecomphcated arrangement ofsteam piping involves condensation losses, and,

steam leakage often arises. In accordance with my present arrangement no steam-is required and a variable speed for each stoker unit is secured without any complicated or costl-y gearing. e x Thus instead of actuating each plunger intermittently by steam, or instead of cone tinuously operating the plungers by a high speed steam engine through speed-reduction gearing and clutch'as described above, 1 ac.--

tu-ate the fanor, fans} and also all the plungers c by the variable speed motor. a

the arrangement being such that, while the fan or fans 6 are continuously rotated, the

to enables each st connected, intermittently, variable, steps. That is't'o say, the

may: be adjusted so as to cause the pawl ggar previously referred 0 er unit to advance the crank-shaft k, to which the plu-n em 0 are in orm, but W -'7" may engage one, two or more teeth of the' y ateach stroke,accordin tothe position of "the shroud 7' (Fig. 5)w 'chdrive the-fan or "fans or turbine a and. to eonnect'th'e fan or fans; .to the stoker driving gear -for"its stoker,'

.' combustible residue to the when oscillated by the rod 2, a) be raised clear of the teeth in the ratchet wheel. The shroud or stop j consists of a flat plate fitted close behind the ratchet wheel 3' while the pawl j "is as wide as the ratchet wheel; and stop combined. The. shroud or stop has a curved portion 7' standing slightly above the teeth of the ratchet wheel 3' adapted to prevent the pawl 7" from engaging the ratchet teeth. The position of the shroud or stop can be varied so that it covers one or more teeth. passed over by the pawland it may be fixed in anw desired position by means of a pin or bolt 7" engaging an extension 3' of the shroud or stop of oneof the holes j" in a quadrant j attachedto' the frame of the stoker ear, see Fig. 5. Or, .the' pawl can be entirely held out of engagement with the ratchet teeth and thereby have an idle motion, thus each stoker unit has a range of. speeds independently'of the other units, and each unit can instantly be brought to rest as desired. I 1 am aware that ratchet mechanism has been used for overfeed stoke'rs notably for retating through worm-gearing thecontinuous grates of chain-gr tokei's, but it has not been used in con action: with underfeed stokers having reciprocating fuel plungers" (with or without reciprocating ash pushers) and in combination with a fan or fans for delivering air under pressure to the twyers of such underfeed stokers.

As shown" in Figs. 3 and-4 each furnace is provided with a fan I) for delivering the air directly into the air chamber below each stoker andthence through the twyers into the fire. A's eachton vof coal burnt requires for its cmnbustion about 450,000 cubic feet of air weighing approximately sixteen tons, the air ducts of the known type, as indicated at Figs. 1 and 2, are bu and costly. They are also subject to air eakage, and the diversion of air from the mam duct or conduit; into branch pipes also causesconsidera'ble frictional loss involving extra power cost. .By providing each stoker with an individual fan b dischargin directly under the stoker, all the cost, 111k and other inconveniences of air ducts and pipes hithertoused are avoided. The power to drive the series of fans I) and plungers c is also re'ferably transmitted mechanically from tlieflmotor a by the shaft n and .sprocket chains 0, o, and chain 0 drivin stokersm and the chain o". the'-fans b. t

would however, be equally practicable in the arrangemeutshownatFigs. 3eand 4, to

see Fig.

:v Provision is also main-ibis ty jof stoker for continuouslydischarging t e init wh le maindirect from the motor stream without leaving suflicient opening for excessive air to flow nto the furnace from the ash-pit. A rack allows of the lever p being set at any pre etermined' position to give the desire ables the position of the plate to be adjusted in a-single motion when required. Further, the plate f can be set either to entirely close the opening and accumulate the ash, or to 'give the maximum opemng when it is de sired to shut down a boiler.

For controllingthe supply of fuel and air in correct proportions in order that the rate of combustion may be automaticall varied in response to the varying deman on the boilers for steam, an hydraulic regulator 8, provided with a piston s and a diaphragm s exposed to steam pressure on its underside is employed. As the load on the boilers increases, the steam pressure drops and the diaphragm 8 falls so that water pressure is admitted to the upper side of the piston s to cause it tobe forced down and thereby raise the lever t of the throttle valve u to speed upthe turbine a, see Figs. 1 and 8. Thus, as the motor or turbine a drives the air supplying fan or fans and also the stoker opening, and the lever en-w mechanisms, the air and the fuel to each fur nace in service is correspondingly increased so that the rate of combustion responds to the demand for steam, or load, on the boilers.

Conversely, as the load falls off, the steam pressure begins to rise, pushing up the diaphragm s and admitting water pressure to raise the piston 8' during which a weight t pulls back the lever 16 of the throttle valve u and reduces the speed of the motor or turbine so that the rate of combustion is reduced to correspond to the falling load, and steady steam pressure and efficient combustion are thus maintained at varying loads.

- What I claim and desire to secure by Letters Patent of the United States is A geared mechanical underfeed stoker for boiler furnaces, comprising retorts, reciprocating fuel feeding lungers, a crank shaft for actuating said p ungers, twyers, an air chamber below the stoker, a fan for supply ing air to said chamber and twyers, means for discharging the ash, intermittent gear associated with said crank shaft for controlling the plungers, a turbine for drivin the crank shaft and fan, a valve for contro ling the admission of steam to said turbine, and a regulator, includin a piston positively actuated by water un er pressure, connected to said valve.

In testimony whereof I afiix my signature in presence of two witnesses.

1 CHARLES ERITH. Witnesses:

GEORGE Enrrn, P. D. summons. 

